Bottles, in particular plastic bottles, cans etc., are often combined to form groups and wrapped with a sheet material in practice and in the daily production sequence. If the sheet material is a plastic sheet material, the sheet material is also shrunk so that the articles form a stable packaging unit and undergo reciprocal fixing with the help of the shrunk sheet material. In this process, open, lateral, so-called shrinkage holes are typically observed.
In the case of a method and associated apparatus of the embodiment described above according to DE 42 07 725 A1, a procedure for this purpose is adopted such that a sheet material carrier bar moves beneath a sheet-material coil. The sheet material carrier bar follows a circular path over the group of articles or the product group, and as it does so, wraps the already mentioned sheet-material coil over this product group. The sheet material carrier bar, together with the trailing end of the sheet material, subsequently descends into a slit of a transporting path. During the onward transport of the product group, which is wrapped in this way, it travels over the slit. As it does so, it also pulls the leading end of the sheet-material coil beneath itself. Consequently, the product group stands on the overlapping ends of the sheet-material coil, the sheet-material overlap. The ends of the sheet material coil or the sheet-material overlap are welded during the subsequent shrinking process.
The described process has generally proven successful but is in need of some improvement insofar as the stability of the produced packaging unit is concerned. It is a fact that the regularly provided side shrinkage holes that are open at both ends result in movement or possible movement, relative to each other, of the articles that are combined to form the packaging unit. This leads to instabilities of the packaging unit, especially if the individual articles are in themselves heavy and/or can be easily displaced against one another. This is typically the case with cans.
The prior art also describes a packaging machine that, according to DE 20 2010 013 513 U1, is to be equipped with a reliably functioning guide facility for strip and sheet material. Associated packaging paths are guided over flat guiding elements for this purpose. At least one of the guiding elements is configured as an ultrasound storage unit. The problems described above in the subsequent use of the packaging unit are not significantly influenced as a result of this.
Comparable comments apply to the machine for the packaging of articles as described in DE 20 2006 020 359 U1. Here, a take-off roll for feeding the sheet material is equipped with at least one textured surface in order to increase the overall functional reliability.